Wheelchairs are commonly used to assist individuals whose ability to walk is impaired, or who are completely unable to walk. When the individual seated in the wheelchair has use of his or her hands, he or she can propel himself or herself in the wheelchair by means of hand rings attached to the rear wheels of the wheelchair. Hand grips are also provided in the rear of the wheelchair to allow a caregiver to push the wheelchair.
When a wheelchair arrives at step, it becomes necessary to raise or lower the wheelchair together with the individual seated in the wheelchair. Various devices have been proposed for facilitating the movement of a wheelchair up or down a step.
U.S. Pat. No. 4,962,942, for example, discloses a wheelchair which can negotiate curbs and other obstructions. The wheelchair has first auxiliary support wheels located between the front and rear wheels, and second auxiliary wheels behind the rear wheels. The front wheels and the rear wheels are structured to be raised or lowered by the wheelchair occupant. When a curb is encountered, the occupant propels the wheelchair forwardly until the first auxiliary wheels are at the edge of the curb, and the front wheels are suspended in air. The front wheels are then lowered to the bottom of the curb and the wheelchair is propelled forward until the second auxiliary wheels are at the curb edge. The large rear wheels are then lowered to curb level, and the wheelchair is propelled by the occupant to the opposite curb, where the curb is ascended by turning the wheelchair 180° and performing the wheel adjusting process in the opposite sequence.
Wheelchairs designed for assisting in negotiating a step are also disclosed in Chinese Patent CN202179644, and U.S. Pat. Nos. 4,811,966, 5,228,709, 8,167,317.